The present invention relates to animal restraining systems and, more particularly, to such systems which employ radio signals and a collar or the like which is worn by the animal and produces warning signals to prevent the animal from straying from a designated area.
Over the years a number of systems have been developed to provide means for limiting the movement of animals to keep them within an area such as a yard. Peck U.S. Pat. No. 3,753,421 describes a system in which a wire is utilized to define the boundary of the area in which the animal is to be restrained, and a current flows through this wire. The animal to be restrained wears a detector on a collar, and it receives a signal from the wire and will generate a warning shock to the animal if the animal approaches too closely to the boundary wire. This system has enjoyed some success, but has a number of limitations including the requirement for a length of exposed or buried wire carrying current and extending about the perimeter of the area.
Brose U.S. Pat. No. 4,898,120, which is assigned to the same assignee as the present invention, discloses a more sophisticated system in which the parameters of the area in which the animal is to be restrained are determined by evaluating a signal received by a central receiver sent from a transmitter on the animal, and this central unit may then transmit a signal to the device worn by the animal to generate a warning shock, sound or the like. This enables a more sophisticated determination of the area in which the animal is free to roam, and avoids the necessity for exposed wires about the perimeter and the like.
It is an object of the present invention to provide a novel system for retraining an animal to a defined area which employs a relatively simple transmitter, and a unit to be worn by the animal which is reactive to the strength of the signals from the transmitter antenna.
It is also an object to provide such a system in which the receiver unit worn by the animal is operative regardless of the orientation of the animal relative to the transmitter antenna and regardless of the presence of other objects about the animal.
Another object is to provide such a system in which the receiver may be fabricated readily from commercially available commercial components and in a relatively miniaturized form.
Still another object is to provide such a system which is reliable in performance and which is relatively long-lived.